Higher Dworshak Flows Continue,by Mike O'Bryant
With weather expected to be hot in eastern Washington and Idaho the remainder of this week, the Nez Perce Tribe and Idaho Fish and Game agreed to keep the cold water flows out of Dworshak Dam at 14,000 cubic feet per second for at least one more week, rather than drop flows to 12 kcfs as they earlier proposed.
That puts off a decision by the Technical Management Team until next week about how augmentation waters from the Dworshak Reservoir should be used this summer.
The choice for TMT is between two system operations requests. One is in keeping with NOAA Fisheries 2000 biological opinion of the Columbia River hydroelectric system that would cut off flow augmentation for the lower Snake River Aug. 24. The other, a plan by both the Nez Perce and Idaho, would spread the benefits of the reservoir's cooling waters to benefit migrating juvenile and adult salmon to mid-September, but flows from Dworshak Dam would have to drop sooner to save water for later.
The 2003 juvenile passage this year peaked around July 1, Paul Wagner of NOAA Fisheries told TMT this week. In fact, more than 90 percent of this year's wild subyearling fall chinook out of the Snake River mainstem has passed through Lower Granite Dam and the trend in passage is declining. That corresponds with work by Billy Connor, fishery biologist at U.S. Fish and Wildlife Service, who has been studying Snake River juvenile passage for a number of years. He also found that the Snake River subyearling chinook migration peaks in July and is mostly over by August 1. He also predicted, in information provided to TMT this week, that the migration would benefit from beginning augmentation flows earlier in July and that additional flows in September would be less beneficial.
"Our point is that it is best to provide the water early in the season," Wagner said of the SOR supported by NOAA Fisheries, the U.S. Fish and Wildlife Service and the states of Oregon and Washington. "The other (the Nez Perce/Idaho plan) says that the early migration affords us the opportunity to use water later in the season."
However, Wagner's estimate doesn't account for chinook juveniles coming out of the Clearwater River, which have a tendency also to peak early but to continue to pass downstream into September.
In addition, Wagner noted that Dworshak water helps cool temperatures in the lower Snake River are until the augmentation stops, then temperatures tend to rise beyond water quality limits. In the past the higher temperatures have lasted to about mid-September. "One SOR recognizes water quality standards throughout the year (the Nez Perce/Idaho plan), while the other focuses (on maintaining water quality standards) during the juvenile passage," Wagner said.
Flows in the lower Snake River now are declining while river temperatures are rising. Even with the cooling effects of 44.7 degree Fahrenheit to 45.7 degree water coming out of Dworshak Dam, forebay temperatures at Lower Granite Dam reached 69-71 degrees this week and the tailwater temperature was 67 degrees. With higher air temperatures expected this week and next, water temperatures could rise even higher.
"From the Nez Perce perspective, we prefer to cut back on outflows after the heat wave moves through," said Kyle Martin, hydrologist for the Columbia River Inter-Tribal Fish Commission. He added that the Nez Perce still wants to reserve water by limiting the draft at Dworshak Reservoir to a 1,435-foot elevation at the end of August and use the remaining flow augmentation water (down to an elevation of 1,420 feet) in September.
The 14 kcfs flow augmentation from Dworshak Reservoir, which began July 9, have caused the dam's elevation to drop from full or about 1,600 feet to 1,589.2 feet earlier this week. Flow this month through Lower Granite is projected by the Corps to be 34 kcfs, far lower than the BiOp target of 50 kcfs for summer flows.
"We've been debating this issue for years and years," said Steve Pettit of the Idaho Department of Fish and Game. "The Idaho position is that this is now an academic debate and should have been addressed in the 2000 BiOp by adding 10 weeks of Dworshak flow augmentation instead of the eight weeks currently in the BiOp.
"All would be happy," he said.
"The reason for the debate is because no one is happy because they recognize that there is not enough water," Wagner said.
The two proposed operations are identical in their early stages, but diverge when the Nez Perce/Idaho proposal would drop flows slightly in order to save water for late summer. The extra week at 14 kcfs agreed to this week by the Nez Perce, however, sets back by one week the period that the two SORs diverge. Originally, the Nez Perce/Idaho SOR proposed dropping flows to 12 kcfs on July 21st, while the BiOp would continue the 14 kcfs flows for as long as possible, which this year could go to Aug. 24, according to calculations by the U.S. Army Corps of Engineers. At that point, the reservoir would be at a 1,520 foot elevation and flows would drop to 1.4 kcfs.
On the other hand, the Nez Perce/Idaho proposal would draft the reservoir to 1,535 feet by the end of August, leaving 200,000 acre feet of augmentation water to be used in September. In addition to dropping Dworshak flows to 12 kcfs July 21 (now July 28), the proposal would drop flows to 11 kcfs Aug. 4, to 10 kcfs Aug. 11, and 8 kcfs Aug. 25, and then it would increase flows slightly to 8.4 kcfs from Sept. 1 to Sept. 15. At that time, flows would drop to 1.4 kcfs as the reservoir reaches an elevation of 1,520 feet.
Technical Management Team: www.nwd-wc.usace.army.mil/TMT/index.html
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